Boot loop after being dropped, now stuck in DFU
My granddaughter's iPhone 7 is now giving me headaches. Other than a small crack in the screen that's been there for a couple of months and hasn't caused any problems, her phone was in pretty good shape.
Was being the operative word here, right up until she took it skateboarding - with a predicable outcome.
After removing the crushed screen protector and finding there wasn't actually any further damage to the screen other than the original crack in the corner, I proceeded to dig in to evaluate the issue. She brought it to me because every time she turns it on, it displays the Apple logo for a minute or so then goes black only to repeat the scenario ad infinitum.
So I opened up the phone and tried every combination and permutation of plugging and unplugging all of the connectors on the motherboard to no effect; nothing I tried made any difference.
Finally I plugged it into a computer and managed to get it into DFU mode. It told me the phone couldn't be updated and had to be restored, so I said fine, go ahead and restore it.
No luck there; it quit with error 4013. I did have a replacement screen that I was holding onto for the inevitable time when the screen took more damage and truly needed replacement, so I went ahead and plugged the replacement screen in and tried the update again with the same results.
Now it no longer boot loops, but comes up in DFU mode every time.
I'm forced to conclude there's probably damage to the logic board and would like some help in determining what my next step should be. I have a certain amount of equipment such as a multimeter, soldering iron, heat gun, etc., at home but I can always go into work and use the professional grade equipment there like microscopes and hot air stations if need be.
At this point I'm considering the possibility of attempting to reflow the audio IC as demonstrated in this guide that actually describes the situation pretty well.
How to fix an iPhone 7 stuck / hanging on a logo - iFixit Repair Guide
However, are there diagnostic steps that I should try first? Things like diode checks? If so, what should I check, and what would I be looking for?
I've worked with circuit boards for about 40 years now and the delicate nature of iPhone logic boards will be a first for me, but I have no problem diving in and giving it my best shot.
I'm tagging @flannelist as the closest to an expert in this area that I'm aware of, but would welcome anyone else who has expertise in this area that's willing to help out.
Update 5/6/2023
Tried connecting with 3uTools. When flashing it gets to 19% after the "Sending KernelCache" part, changes to "Restoring", then fails with "ERROR: Device failed to enter restore mode."
Interestingly, when I click on the "Exit Recovery Mode" button on the Device page, it actually does exit DFU and goes back to its reboot cycle. Afterwards I put it back in DFU mode and it stays there.
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5 opmerkingen
@dadibrokeit I see you. I'm just finishing a stint of nitpicking a bunch of wikis and my brain is done for the night. But I will give this a good read in the morning. Or when I my brain remembers at 2am and can't let it go.
door Alisha C
@flannelist Thanks Alisha, no rush - I slapped together an iPhone X with a bad proximity detector and a busted screen for my granddaughter so she's got a perfectly good phone to use for the foreseeable future.
door Jerry Wheeler
@dadibrokeit
Hi!
Just until @flannelist get back to you I have some more info...
you mentioned that the phone was dropped so it could be the audio ic as you mentioned but it could also Nand related as bad Nand or a fault on that area can give a boot loop from what iv seen...it might be worth checking if there any any components missing from after the drop...I usually do this by comparing a image from ifixits teardown to the board infront of me
Demontage van de iPhone 7
step13 to 16
just thought I would pass this by just to help with the process of elimination :-)
door HelloMacOS
@hellomacos That is a good point. At the very least I should be able to check the components on the top side of the board; on the bottom they're covered by some sort of insulating sheet so I'll probably hold off on removing those unless I get to a point where there's nothing else to do.
door Jerry Wheeler
@dadibrokeit
Yeah I would definitely leave that as a last resort
Best not to apply heat and possibly make the issue worse
door HelloMacOS